Switching From "Full-" To "Shorter-Season" Corn Hybrids

May 27, 1999 6(10):59-60

Joe Lauer, Corn Agronomist

According to the May 23 report from the Wisconsin Agricultural Statistics Service
about 86% of the corn acres is planted. On those acres that still need to be planted,
farmers are considering whether or not to switch to shorter-season hybrids.

A four-year trial was conducted at Lancaster, Arlington, Hancock, Marshfield, Spooner,
and Ashland between 1991 and 1994. In these trials both full- and shorter-season
hybrids were planted. The shorter-season hybrid differed from the full-season hybrid
by 5 to 7 relative maturity units (days). Corn price ($2.00, 2.75, and 3.50 per
bushel) and drying ($0.00, 0.015 and 0.03 per bushel), hauling ($0.04 per bushel),
and handling ($0.017 per bushel) costs were all factored into the economic model
used to determine switch dates between the full- and shorter-season hybrids.

Corn grain yield was found to decrease about 0.3-0.5% per day during early May.
The rate of grain yield decrease accelerated to 1.5-2.3% per day when corn was planted
later in May.

Drying cost (or the type of corn production system) was most important factor in
determining switch date between full - and shorter- season hybrids (Table 1). If
corn drying costs are relatively expensive (i.e. drying at a commercial elevator),
then switch dates were 7 to 11 days earlier than corn used as high moisture corn
in a livestock system or in years when there are no drying costs.

Table 1. Date to switch corn hybrids from full- to shorter- season relative maturity
in three corn production systems.

Corn production system

Drying cost
per bushel

Average for Marshfield,
Spooner, Ashland

Average for Lancaster,
Arlington, Hancock

Commercial elevator drying

$0.03

May 18

May 2

On-Farm drying

$0.015

May 23

May 6

Livestock (high moisture corn)

$0.00

May 25

May 13

Corn price had no influence on switch date in a livestock system. In an on-farm
drying system low corn prices required switch dates 1 to 3 days earlier at $2.00
corn compared to $3.50 corn. Corn price became increasingly important in the commercial
elevator drying system. Depending upon location, switch dates needed to occur 2
to 9 days earlier with $2.00 corn than with $3.50 corn.

Field conditions: Although the penalty for late planting is important, growers
also need to be careful to avoid tillage when soil is too wet. Yields may be reduced
somewhat this year, but effects of soil compaction can reduce yields for several
years to come.

Hybrid dry-down and grain quality characteristics: Longer-season hybrids
within the latest acceptable planting dates should have fast grain dry-down and
high test weight characteristics. Growing season, site and management influence
a particular hybrid's actual days to maturity.

Ease of trading original hybrids for superior shorter-season alternatives.<